The overall goal of the proposed research is to better understand the complex mechanisms that control nervous system development through a series of experiments concerned with the normal prenatal and postnatal development of visual system neurons. While the proposed studies will provide new information regarding development of the visual system, the scope of these investigations is such that the findings will also provide very direct insights into nervous system development as a whole. Defining the crucial events in normal nervous system development could have far reaching implications for a variety of developmental disorders of the nervous system. The rationale underlying the proposed research is that neurons destined to exhibit certain structural characteristics can be identified at virtually any point in development if either their birthdates or antigenic properties are distinct, and that this early identification of different cell types makes it possible to provide very complete developmental histories for each class of neuron. Such histories can, in turn, provide insights into the structural and functional differences exhibited by neurons and the developmental events that contribute to such differences. Attaining the overall goal of the research requires three separate, but related, experimental approaches: the first utilizing 3H-thymidine autoradiographic techniques to define neuronal birthdates, the second utilizing immunologic techniques to define the antigenic determinants of neurons with the same birthdates and/or similar structural characteristics, and the third utilizing teratologic agents to selectively destroy distinct populations of developing cortical cells.